The Regency era of British history is commonly understood as the years between c. 1795 and 1837, although the official regency for which it is named only spanned the years 1811 to 1820. King George III first suffered debilitating illness in the late 1780s, and relapsed into his final mental illness in 1810. By the Regency Act 1811, his eldest son George, Prince of Wales, was appointed Prince Regent to discharge royal functions. The Prince had been a major force in Society for decades. When George III died in 1820, the Prince Regent succeeded him as George IV. In terms of periodisation, the longer timespan is roughly the final third of the Georgian era (1714–1837), encompassing the last 25 years or so of George III's reign, including the official Regency, and the complete reigns of both George IV and his brother and successor William IV. It ends with the accession of Queen Victoria in June 1837 and is followed by the Victorian era (1837–1901).